[PATCH] tpm_tis: Check for an error after exhausting send retires

[Jacqueline Wong <jacqwong@google.com>]

From: Jordan Hand <jhand@google.com>

tpm_tis_send_main() will attempt to retry sending data TPM_RETRY times.
Currently, if those retries are exhausted, the driver will attempt to
call execute. The TPM will be in the wrong state, leading to the
operation simply timing out.

Instead, if there is still an error after retries are exhausted, return
that error immediately.

Additionally, add logging to more easily determine reason for transmit
failure.

Fixes: 280db21e153d8 ("tpm_tis: Resend command to recover from data transfer errors")
Signed-off-by: Jordan Hand <jhand@google.com>
---
 drivers/char/tpm/tpm_tis_core.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/char/tpm/tpm_tis_core.c b/drivers/char/tpm/tpm_tis_core.c
index e2a1769081b1..b78937841879 100644
--- a/drivers/char/tpm/tpm_tis_core.c
+++ b/drivers/char/tpm/tpm_tis_core.c
@@ -471,6 +471,8 @@ static int tpm_tis_send_data(struct tpm_chip *chip, const u8 *buf, size_t len)
 		status = tpm_tis_status(chip);
 		if (!itpm && (status & TPM_STS_DATA_EXPECT) == 0) {
 			rc = -EIO;
+			dev_err(&chip->dev, "TPM_STS_DATA_EXPECT should be set. sts = 0x%08x\n",
+					status);
 			goto out_err;
 		}
 	}
@@ -491,6 +493,8 @@ static int tpm_tis_send_data(struct tpm_chip *chip, const u8 *buf, size_t len)
 	status = tpm_tis_status(chip);
 	if (!itpm && (status & TPM_STS_DATA_EXPECT) != 0) {
 		rc = -EIO;
+		dev_err(&chip->dev, "TPM_STS_DATA_EXPECT should be unset. sts = 0x%08x\n",
+				status);
 		goto out_err;
 	}
 
@@ -552,11 +556,16 @@ static int tpm_tis_send_main(struct tpm_chip *chip, const u8 *buf, size_t len)
 			break;
 		else if (rc != -EAGAIN && rc != -EIO)
 			/* Data transfer failed, not recoverable */
-			return rc;
+			goto out_err;
 
 		usleep_range(priv->timeout_min, priv->timeout_max);
 	}
 
+	if (rc == -EAGAIN || rc == -EIO) {
+		dev_err(&chip->dev, "Exhausted tpm_tis_send_data retries\n");
+		goto out_err;
+	}
+
 	/* go and do it */
 	rc = tpm_tis_write8(priv, TPM_STS(priv->locality), TPM_STS_GO);
 	if (rc < 0)
-- 
2.53.0.1213.gd9a14994de-goog